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I HAVE A PROBLUM WITH A NEW 5 TON SYSTEM GOING THROUGH COMPRESSORS DUE TO 29 DEGREE EVAPORATOR. I DID NOT INSTALL IT , JUST TRYING TO CURE PROBLUM. IT HAS A 20X40 RETURN AND PLEUM WITH EIGHT 8in. DROPS. STATIC PRESSURE AT RETURN IS .25, STASTIC AT SUPPLY IS .20. I CHECKED BLOWER SIZE, SPEED, AND ROTATION AND ALL CHECKS OKAY. IT USES A FLO-RATOR #82 AND AM RUNNING A 10 -12 SYSTEM SUPER HEAT. THE SUCTION LINE IS A LITTLE SMALL 3/4 INSTEAD OF 7/8 , BUT NOT ENOUGH TO CAUSE THIS. THE SUCTION LINE RUN IS ONLY 6FT. THE ONLY THING I DID NOT DO YET IS DISCONNECT THE BLOWER AND CHECK FOR FROST PATTERN ON EVAP. ANY IDEARS?

Those static pressure readings can't be correct, at least not in inches of water. A standard blower in a residential unit could never generate those pressures under any conditions.

What are the return and supply air temperatures?

If your return air temperature is low, the 29 degree evaperator temperature could be normal.

What is your subcooling?

Make sure the orifice is the correct size listed for the outdoor unit. A #82 orifice seems small for a 5 ton system. That is a size I would expect to find in a 4 ton, or a high efficiency 3.5 ton system.

1 sq. ft of return per ton. what is the size of your supply duct? 8 8" drops @ 200 cfm each is 1600 cfm which is a little low but not bad but we still need to know if you are actually getting that to those drops either way it is an airflow problem and it sounds like you need to look at the supply before you seperate the blower wheel

Learning never ends and everyone has something to teach. Some people teach me what to be like others teach me what not to be like!

HELLO ......... 1 deg of sub cooling ???? your low on gas period your coil is empty so either you have a discharge line restriction ( which i doubt) or your under charged but now lets be fair.... what is your superheat... if your at 25 or more add gas.

Originally posted by coldboy I HAVE A PROBLUM WITH A NEW 5 TON SYSTEM GOING THROUGH COMPRESSORS DUE TO 29 DEGREE EVAPORATOR. I DID NOT INSTALL IT , JUST TRYING TO CURE PROBLUM. IT HAS A 20X40 RETURN AND PLEUM WITH EIGHT 8in. DROPS. STATIC PRESSURE AT RETURN IS .25, STASTIC AT SUPPLY IS .20. I CHECKED BLOWER SIZE, SPEED, AND ROTATION AND ALL CHECKS OKAY. IT USES A FLO-RATOR #82 AND AM RUNNING A 10 -12 SYSTEM SUPER HEAT. THE SUCTION LINE IS A LITTLE SMALL 3/4 INSTEAD OF 7/8 , BUT NOT ENOUGH TO CAUSE THIS. THE SUCTION LINE RUN IS ONLY 6FT. THE ONLY THING I DID NOT DO YET IS DISCONNECT THE BLOWER AND CHECK FOR FROST PATTERN ON EVAP. ANY IDEARS?

[Edited by coldboy on 03-30-2005 at 06:18 PM]

You're measuring one degree of subcooling and between 10-12 superheat? What were the indoor and outdoor conditions (temperatures) like when you took these readings?

How many compressors has this system eaten?

What is your temperature drop across the indoor coil?

Only thing I can figure at this late hour (and drooping eyes) is possible undercharge combined with poor airflow. Undercharge would explain low subcoooling and poor airflow would explain why superheat reads 10-12 vs. something a lot higher for an undercharge condition.

How are you sure the other compressor(s) were lost from the symptoms you're seeing now? Could've been for a different reason and the last person that worked on it created a new set of problems with his repair methods.

Outdoor Air Temperature
Indoor Air temperature
Return Air temperature
Supply Air Temperature
Actual Airflow (right now we have .45" total static)We want actual airflow.
Suction Pressure
Head Pressure
Suction line temperature at unit
Suction line temperature at indoor coil
Liquid Line temperature at unit
Liquid Line temperature at indoor coil.
Calculate Superheat at outdoor unit
Caluclate Subcooling at outdoor unit.
Measure liquid line leaving condenser.
Provide Line size for Liquid Line
Provide Line size for Suction line
Provide Line set total length
Provide the vertical seperation
Is the indoor unit above or below the unit.

Include Outdoor unit Model Number
Include Indoor Air Handler Model Number
Include Indoor Coil Model Number.

Provide accurate info and we can tell you what's wrong.
We'll figure out how to bill it later.